Objective,2,To study the plasma protein binding rates of bufalin, cinobufagin and resibufogenin in different kinds of toad skin extracts.,Methods,2,The plasma protein binding rates of bufalin, cinobufagin and resibufogenin in two extracts of toad skin and control solution with different concentrations of bufogenin, cinobufagin and cinobufagin were determined by equilibrium dialysis and LC-MS/MS method.,Results,2,The LC-MS/MS method showed good linearity, the accuracy, precision, recovery and stability of the analytes all met the methodology requirements. The plasma protein binding rates of bufalin in three different concentrations of control solution and in two kinds of toad skin extracts were (75.03±1.97) %, (72.33±2.51) %, (71.80±1.53) %, (-16.67±1.58) % and (71.93±1.48) %, respectively. The plasma protein binding rates of cinobufagin in three different concentrations of control solutionand in two kinds of toad skin extracts were (52.33±4.13) %, (52.47±3.84) %, (47.60±2.46) %, (-51.23±3.53) % and (40.93±1.29) %, respectively. The plasma protein binding rates of resibufogenin in three concentrations of control solution and in two kinds of toad skin extracts were (91.27±1.09) %, (93.60±0.85) %, (88.13±0.76) %, (52.67±3.58) % and (80.13±2.38) %, respectively.,Conclusions,2,The results show that the plasma protein binding rates of bufalin, cinobufagin and resibufogenin are not dependent on the drug concentration. The plasma protein binding rates of them in extract 1 are significantly lower than those of control solution, while the plasma protein binding rates of them in toad skin extract 2 are basically the same as those of the control solution. It is suggested the mixture system of toad skin extract 1 leads to the change of plasma protein binding rates of bufalin, cinobufagin and resibufogenin.